July 28, 2015 – Investigators with the Kentucky State Fire Marshal’s office have ruled the April 24 explosion at the Silver Trail Distillery an accident, but blame a pressure relief valve as a likely cause of the blast that killed one distiller and critically injured a second. The still was built in 2011 by Revenoor Stills of Yamhill, Oregon, and during an exclusive WhiskyCast interview May 22, Revenoor owner Terry Wilhelm said his stills were not designed to be pressurized. However, Wilhelm told investigators he installs pressure relief valves “to keep the lawyers away” and to serve as a backup in case a clog backs up the still output. According to the investigative report, Wilhelm said welds on his stills would start to crack at 4-5psi (pounds per square inch of pressure) before the pressure valve activated. By way of comparison, a properly-inflated NFL football is filled with approximately 13psi of air.

A Watts LLL100XL pressure relief valve similar to the one installed on the Silver Trail Distillery still. Image courtesy Watts Water Technologies.However, the valve installed on Silver Trail’s still was never designed to be used with a still. The Watts LLL100XL pressure relief valve is designed for use on home water heaters, according to the company’s documentation. That model is set for 210º Fahrenheit, and has a pressure relief range of 75-150psi. The valve is commonly available from plumbing suppliers, and sells for around $22 online, though WhiskyCast was able to find it at a major home improvement store for $12.50. Quoting from the report:

“Being that the still was not designed or intended to be a pressure vessel, a pressure relief valve rated at 150psi appears very excessive.”

Jay Rogers, who survived the explosion but suffered critical burns, told investigators the pot still had been operating at around 202º at the time of the explosion. While the investigation found no signs of a blast wave or propane explosion, the still was blown clear of the building. The copper pot was found about 50 feet away, while the 4″ diameter column landed about 72 feet from the building and the stainless steel access lid for the pot still landed 95 feet away. Jay and Kyle Rogers, who died 17 days later from his burns, had already produced at least three gallons of moonshine that morning with no signs of clogs in the still’s output.

“All indications are that the event directly involved the over pressurization of the still with subsequent failure which resulted in it being propelled out the north end of the structure.”

What caused the pressure buildup inside that still? While the investigation does not list an exact cause, the design of the still uses glass marbles in the column to increase the surface area for condensing water. The report notes that those marbles can also reduce the flow of spirit through the column and increase pressure, especially if the mash inside the still has suspended solids that can clog up flow through the marbles. Silver Trail founder Spencer Balentine has previously told WhiskyCast that was unlikely, since the distillery’s practice is to filter its mash three times to remove any solids before filling it into the still. However, Balentine and Jay Rogers told Deputy Fire Marshal Bill Compton that they had recently found a marble stuck inside a hole in the plate that keeps the marbles from falling out of the still while allowing vapor to rise through the column. They freed the marble by pushing water through the column while tapping the side with a rubber mallet.

In a statement, Balentine said “Basically it verifies that the tower failed due to an internal plate being only tack welded when it should have been welded fully around. This allowed a distilling bean or beans (glass marbles) to clog the product (shine) output hole. This caused an immediate over pressurization which ruptured the still bottom and sent it hurtling through the door.” It should be noted that the Fire Marshal’s report does not mention the welding issues raised in Balentine’s statement.

While there were no links between the distillery’s propane service and the explosion, the report did point out several safety-related issues. The Revenoor still was designed originally to be used with electric heat, though Wilhelm told investigators there were no issues with using propane. However, the burners used on the still were rated for outdoor use only and did not have the safety shutoffs required by building codes for indoor use. In addition, the contractor who installed the burners and propane equipment did not have the proper state license as required by law. That same contractor also repaired a split welding seam in the copper pot still shortly after it was installed at Silver Trail, but the repair work was not considered to be related to the April 24 explosion.

While the Fire Marshal’s report ruled the incident an accident, Silver Trail and Jay Rogers have already filed a lawsuit against Terry Wilhelm and Revenoor Stills for civil damages, and Spencer Balentine is asking state prosecutors to present the case to a grand jury for possible criminal charges.

In an August 9 email, Terry Wilhelm declined to comment on the Fire Marshal’s findings.

Editor’s note: This story was updated on August 9 to include a response from Terry Wilhelm of Revenuer Stills, along with our finding the Watts pressure relief valve selling at a lower retail price than originally cited in this story. The May 22 telephone interview we conducted with Terry Wilhelm of Revenoor Stills was cited in the Fire Marshal’s report and is included in the exhibits that are included in the case file. We have also provided a link to download the report from our web site, and the report is also available at the State Fire Marshal’s web site. 

Links: Silver Trail Distillery | Revenoor Stills | Kentucky State Fire Marshal